1. Field of the Invention
The present invention relates to an internal combustion engine having an exhaust device and a method for controlling the internal combustion engine.
2. Background Information
In some conventional internal combustion engines having an exhaust device, a main catalytic converter is arranged on a relatively downstream side in an exhaust system underneath a floor panel or the like of a vehicle. Thus, a thorough exhaust purification effect cannot be expected before the catalytic converter is activated after the temperature of the catalytic converter starts rising upon cold starting of the internal combustion engine. However, if the catalytic converter is arranged in a position closer to the internal combustion engine on a relatively upstream side in the exhaust system, a reduced endurance of the catalytic converter becomes a problem due to thermal aging of a catalyst.
Therefore, Japanese Laid-Open Patent Application Publication No. 5-321644 discloses a conventional exhaust device for an internal combustion engine in which a main catalytic converter is disposed in a main exhaust passage, and an additional bypass catalytic converter is disposed in a bypass passage that is provided in parallel with an upstream portion of the main passage with respect to the main catalytic converter. This conventional exhaust device is configured to selectively guide exhaust gas to the side of the bypass passage immediately after the cold starting by controlling a switching valve that is configured to switch between the main passage and the bypass passage. In this conventional exhaust device, the bypass catalytic converter is disposed in a position relatively closer to the upstream side (i.e., closer to the internal combustion engine) in the exhaust system than the main catalytic converter. Therefore, exhaust gas purification can be started from an earlier stage by the bypass catalytic converter, since the bypass catalytic converter is activated relatively early as compared to the main catalytic converter.